JP2009238329A - Optical disk unit and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably control driving an objective lens while suppressing mutual interference between tilt control and focus control for the objective lens on an optical head. <P>SOLUTION: An optical disk unit comprises an actuator for imparting driving forces f<SB>1</SB>and f<SB>2</SB>respectively to opposite first- and second-driven positions P<SB>1</SB>and P<SB>2</SB>on the objective lens unit via a centroid G of the objective lens unit sandwiched from the direction orthogonal to the light axis of the objective lens, and a focus/tilt control circuit for adjusting distribution of the driving forces f<SB>1</SB>and f<SB>2</SB>imparted respectively to the driven positions P<SB>1</SB>and P<SB>2</SB>to avoid influence of the displacement power in the tilt direction θ at the centroid G on the displacement power in the focusing direction y when the displacement power in the tilt direction θ and focusing direction y acts on the objective lens unit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that reproduces or records information using an optical disc and a control method thereof.

  There is known an optical disc apparatus that uses two types of focus coils provided in an objective lens drive mechanism on an optical head to perform objective lens focus control and objective lens tilt correction by feedforward control (for example, Patent Document 1).

In addition, the tilt value of the objective lens can be controlled by correcting the current value to be supplied to the two focus coils in a manner that reflects the difference in the detected tilt value of the objective lens detected at different radial positions on the optical disk. An optical disk device with improved features has also been proposed (see, for example, Patent Document 2).
JP 2005-521985 Publication JP 2003-272203 A

  However, the techniques of the above-described documents have a configuration in which it is difficult to appropriately drive and control the objective lens because the control of the objective lens in the tilt direction and the control in the focus direction interfere with each other.

  Accordingly, the present invention has been made to solve the above-described problem, and an optical disc capable of realizing suitable drive control of an objective lens while suppressing mutual interference between tilt control and focus control of the objective lens on the optical head. An object is to provide an apparatus and a control method thereof.

  In order to solve the above-described problems, the present invention includes an objective lens unit in which an objective lens and a lens holder are integrated, an elastic support member that supports the objective lens unit so as to be displaceable on an optical head body, and the elastic With a driving efficiency equal to the first and second driven positions on the objective lens unit facing each other with the center of gravity position of the objective lens unit supported by the support member sandwiched from the direction orthogonal to the optical axis of the objective lens. The first and second driving units that respectively apply driving force, and the displacement force in the focusing direction at the center of gravity position when the displacement force in the tilt direction and the focusing direction is applied to the objective lens unit is the tilt direction. The first and second driving units respectively apply the first and second driven positions so as to avoid the possible influence on the displacement force of the first and second driving positions. To provide an optical disk apparatus including a driving force adjustment unit that adjusts the distribution of the driving force.

  In order to solve the above-described problem, the present invention sandwiches the position of the center of gravity of an objective lens unit having an objective lens supported so as to be displaceable on the optical head body from a direction perpendicular to the optical axis of the objective lens. A step of setting a driving force to be applied to each of the first and second driven positions on the objective lens unit facing each other with equal driving efficiency, and a displacement force in the tilt direction and the focusing direction is applied Adjusting the distribution of the set driving force so as to avoid the influence that the displacement force in the focusing direction at the center of gravity position may have on the displacement force in the tilt direction; and each drive in which the distribution is adjusted And a method of controlling the optical disk apparatus, the method including applying a force to the first and second driven positions, respectively.

  According to the present invention, there is provided an optical disc apparatus capable of realizing suitable drive control of an objective lens while suppressing mutual interference between tilt control and focus control of the objective lens on the optical head, and a control method therefor can do.

The best mode for carrying out the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram functionally showing the configuration of the optical disc apparatus 1 according to the first embodiment of the present invention. FIG. 2 is a diagram schematically showing the structure of the optical head 65 mounted on the optical disc apparatus 1. FIG. 3 is a block diagram functionally showing the configuration of the focus / tilt control circuit 87 and the first and second driving force generation circuits 51 and 52 provided in the optical disc apparatus 1.

  As shown in FIGS. 1 and 3, the optical disc apparatus 1 of this embodiment includes an optical head 65, a spindle motor 63, a feed motor 67, a spindle motor control circuit 64, a feed motor control circuit 68, an RF amplifier 85, and a PLL control circuit. 76, data reproduction circuit 78, track control circuit 88, focus / tilt control circuit 87, first and second driving force generation circuits 51 and 52, signal bus 89, CPU 90, RAM 91, ROM 92, NV-RAM 99, error correction circuit 62 etc. are mainly provided. Such an optical disk device 1 is connected to a host device 94 via a predetermined interface circuit 93.

  That is, the optical disc apparatus 1 reproduces and / or records information using an optical disc 100 such as an HD DVD (High Definition Digital Versatile Disc) or a BD (Ble-ray Disc) as an information storage medium. The optical disc 100 has grooves concentrically or spirally formed on the information recording surface 100a shown in FIG. A concave portion of such a groove of the optical disc 100 is called a land, a convex portion is called a groove, and one round of the groove or land is called a track. User data is recorded by irradiating intensity-modulated laser light along the tracks (grooves only or grooves and lands) to form recording marks.

  Data reproduction is performed by irradiating a laser beam with a read power weaker than that at the time of recording along the track and detecting a change in reflected light intensity caused by a recording mark on the track. The recorded data is erased by irradiating a laser beam of erase power stronger than the read power along the track to crystallize the recording layer.

  As shown in FIG. 1, the optical disk 100 is rotationally driven by a spindle motor 63 that functions as a disk rotation driving unit. A rotation angle signal is obtained from a rotary encoder 63 a provided in the spindle motor 63. As the rotation angle signal, when the spindle motor 63 makes one rotation, for example, a pulse signal of 5 pulses is generated. The rotation angle and the number of rotations of the spindle motor 63 can be detected from this rotation angle signal.

  The optical head 65 described above includes an objective lens 70, an objective lens unit 74, first to third actuators 71, 72, 73, a laser diode 79, and a laser modulation control circuit 75, as shown in FIGS. , Half mirror 96, FM-PD 95, collimator lens 80, half prism 81, condenser lens 82, cylindrical lens 83, photodetector 84, and the like.

  That is, recording and reproduction of information with respect to the optical disc 100 is performed by the optical head (optical pickup) 65. The optical head 65 is connected to a feed motor 67 through a gear 60 and a screw shaft 61. The feed motor 67 is driven by a feed motor control circuit 68. That is, the optical head 65 moves in the radial direction of the optical disc 100 by rotating the feed motor 67 by the feed motor drive current from the feed motor control circuit 68.

  As shown in FIG. 2, the optical head 65 is provided with an objective lens unit 74 in which the objective lens 70 and a lens holder 74a for holding the objective lens 70 are integrated. The objective lens unit 74 is movably supported on the optical head 65 main body (head base) via an elastically deformable elastic support member 59 such as a suspension wire or a leaf spring.

  Here, the first and second driving force generation circuits 51 and 52 functioning as the first and second driving units are configured by the first and second magnetic circuits 57 as shown in FIGS. , 58, and first and second actuators 71 and 72, and first and second drive current circuits 97 and 98, respectively. The first and second drive current circuits 97 and 98 output a drive current having a value corresponding to the voltage value of the input signal. The first and second actuators 71 and 72 generate driving forces corresponding to the values of the driving currents output from the first and second driving current circuits 97 and 98, respectively.

  That is, as shown in FIG. 3, the actuators 71 and 72 constitute first and second magnetic circuits 57 and 58 by magnets 55 and 56 for magnetic drive and coils 53 and 54, respectively. A driving force for driving the objective lens unit 74 in a predetermined direction is generated by a Lorentz force generated by supplying a driving current from the first and second driving current circuits 97 and 98 to the coils 53 and 54. Similarly, the third actuator 73 has a magnetic circuit composed of a magnet and a coil for magnetic drive.

More specifically, as shown in FIGS. 1 to 3, the first and second driving force generation circuits 51, 52 having the actuators 71, 72 are provided on the objective lens unit 74 supported by the elastic support member 59. The first and second driven positions P ₁ and P ₂ on the objective lens unit 74 facing each other across the center of gravity position G from a direction x (radial direction in this embodiment) orthogonal to the optical axis s1 of the objective lens. Apply driving force respectively.

That is, as shown in FIGS. 2 and 3, the first and second drive current circuits 97 and 98 supply drive currents having, for example, equal current values to the coils 53 and 54 of the magnetic circuits 57 and 58, for example. in, as shown in FIG. 2, the focusing direction y along the optical axis s ₁ of the objective lens 70, it is possible to move the objective lens unit 74 on the optical head 65 (objective lens 70). On the other hand, the first and second drive current circuits 97 and 98 supply drive currents having different current values to the coils 53 and 54 of the magnetic circuits 57 and 58, for example, to the information storage surface 100a of the optical disc. to drive the direction in which the optical axis s ₁ of the objective lens 70 is tilted tilt direction θ to the objective lens unit 74 is also made of a (optical axis s ₁ is a direction inclined to the optical axis s ₂₎ (objective lens 70) Te Is possible. Furthermore, by supplying a predetermined drive current to the drive coil of the magnetic circuit provided in the actuator 73, the objective lens unit 74 can be moved in the tracking direction (radial direction) x along the radial direction of the optical disc 100. is there. Note that θ in FIG. 2 represents a deviation angle between the optical axis s ₂ of the objective lens 70 and the focusing direction y as seen from the tangential direction d.

Here, in the optical head 65 of the present embodiment, as shown in FIG. 2, the first and second driven positions P ₁ and P ₂ facing each other with the center of gravity G of the objective lens unit 74 sandwiched from the radial direction x. Thus, the driving force in the focus direction y is applied. For this reason, the tilt direction of the objective lens 70 that can be moved and controlled by the actuators 71 and 72 is the radial tilt direction. Here, instead of the actuators 71 and 72, for example, the center of gravity position G of the objective lens unit 74 is disposed so as to apply a driving force in the focus direction y from two driven positions facing each other across the tangential direction d. A pair of actuators may be provided. In this case, the tilt direction of the controllable objective lens 70 is the tangential tilt direction. Furthermore, an optical head capable of driving and controlling the objective lens 70 in each of the radial tilt direction and the tangential tilt direction may be configured by arranging a pair of actuators at an intermediate position between them.

  The laser modulation control circuit 75 sends a write signal to a laser diode (laser light emitting element) 79 based on recording data sent from the host device 94 via the interface circuit 93 during information recording (record mark formation). To supply. Further, the laser modulation control circuit 75 supplies a read signal (with a drive current smaller than the write signal) to the laser diode 79 when reading information.

  In addition, the optical head 65 includes an FM-PD 95 configured by a photodiode. The FM-PD 95 branches a part of the laser light generated by the laser diode 79 by a half mirror 96 by a certain ratio, detects a light reception signal proportional to the light amount, that is, the irradiation power, and converts the light reception signal into a laser modulation control circuit 75. To supply. Based on the light reception signal from the FM-PD 95, the laser modulation control circuit 75 controls the laser diode 79 so that the laser light is emitted at a laser power suitable for reproduction, recording, and data erasing set by the CPU 90, respectively. Control.

  The laser diode 79 generates laser light in accordance with a signal supplied from the laser modulation control circuit 75. Laser light emitted from the laser diode 79 is irradiated onto the optical disc 100 via the collimator lens 80, the half prism 81, and the objective lens 70. The reflected light from the optical disc 100 is guided to the photodetector 84 through the objective lens 70, the half prism 81, the condenser lens 82, and the cylindrical lens 83.

  The photodetector 84 is composed of, for example, four-divided photodetection cells, and detection signals from these photodetection cells are output to the RF amplifier 85. The RF amplifier 85 processes a signal from the photodetection cell, a focus error signal indicating an error from the just focus, a tracking error signal indicating an error between the laser beam spot center and the track center, and a photodetection cell signal. A reproduction signal (RF signal) that is a full addition signal is generated. That is, as shown in FIGS. 1 and 2, the RF amplifier 85 is a position in the focus direction between the information recording surface 100 a of the optical disk 100 that is rotationally driven by the spindle motor 63 and the focal position of the objective lens 70 on the optical head 65. It has a function as a focus error signal output circuit that outputs a focus error signal indicating deviation.

  The focus error signal is supplied to the focus / tilt control circuit 87. As shown in FIG. 2, the focus / tilt control circuit 87 corrects the positional deviation in the focus direction between the information recording surface 100a of the optical disk 100 that is rotationally driven by the spindle motor 63 and the focal position of the objective lens on the optical head. A focus drive signal having a value corresponding to the correction amount for generating the focus drive signal is generated. This focus drive signal is supplied to drive force generation circuits 51 and 52 that drive the objective lens unit 74 on the head 65, so that the laser beam is always focused on the recording film of the information recording surface 100 a of the optical disc 100. Focus servo is performed.

  Further, as shown in FIGS. 1 and 3, the CPU 90 supplies a tilt error signal described later to the focus / tilt control circuit 87 via the signal bus 89 in order to correct the objective lens 70. The focus / tilt control circuit 87 supplies a drive signal obtained by adding a later-described tilt drive signal to the focus drive signal to the drive force generation circuits 51 and 52.

  The tracking error signal is supplied to the track control circuit 88. The track control circuit 88 generates a track drive signal according to the tracking error signal. The track drive signal (track drive current) output from the track control circuit 88 is supplied to the third actuator 73 side. As a result, tracking servo is performed in which the laser beam always traces on the track formed on the optical disc 100.

  By performing the focus servo and the tracking servo, the full addition signal of the output signal of each light detection cell of the light detector 84 is obtained from a pit formed on the track of the optical disc 100 corresponding to the recording information. Reflected light changes are reflected. This signal is supplied to the data reproduction circuit 78. The data reproduction circuit 78 reproduces recorded data based on the reproduction clock signal from the PLL control circuit 76.

  When the objective lens 70 is controlled by the track control circuit 88, the feed motor control circuit 68 controls the feed motor 67, that is, the optical head 65, so that the objective lens 70 is positioned in the vicinity of a predetermined position in the optical head 65. The

  The spindle motor control circuit 64, feed motor control circuit 68, laser modulation control circuit 75, PLL control circuit 76, data reproduction circuit 78, focus / tilt control circuit 87, track control circuit 88, error correction circuit 62, etc. It is controlled by the CPU 90 via the bus 89. The CPU 90 comprehensively controls the main body of the optical disc device 1 in accordance with an operation command provided from the host device 94 via the interface circuit 93. Further, the CPU 90 uses the RAM 91 as a work area and operates according to a control program recorded in the ROM 92 while appropriately referring to various parameters for each device, for example, recorded in the NV-RAM 99 constituted by a nonvolatile memory. To do.

Here, based on FIG. 2, the effect | action which arises in the objective lens unit 74 driven through the actuators 71 and 72 of the driving force generation circuits 51 and 52 is demonstrated. In FIG. 2, the straight line connecting the above-mentioned driven positions (starting points) P ₁ and P ₂ and the optical axis s ₁ are perpendicular to each other at 90 ° and on the straight line connecting the driven positions P ₁ and P _2. In the following description, it is assumed that the gravity center position G of the objective lens unit 74 (holding the objective lens 70) exists.

That is, as shown in FIG. 3, by supplying drive signal currents i ₁ and i ₂ to the coils 53 and 54 of the first and second actuators 71 and 72, respectively, as shown in FIG. Driving forces (Lorentz forces) f ₁ , f in a direction parallel to the focusing direction y along the optical axis s ₁ of the objective lens 70 on the optical head 65 immediately above the driven positions P ₁ , P ₂ on 71, 72. ₂ occurs. Accordingly, as described above, the objective lens unit 74 can be driven in the focusing direction y and the tilt direction θ. The relationship between the drive signal currents i ₁ and i ₂ and the drive forces f ₁ and f ₂ is given by the following equation when the constants determined by the physical properties of the optical head 65 are H ₁ and H ₂ .

f ₁ = H ₁ × i ₁
f ₂ = H ₂ × i ₂
In the optical head 65 of the present embodiment, the distances from the driven positions P ₁ and P ₂ to which the driving forces f ₁ and f ₂ are applied by the actuators 71 and 72 to the gravity center position G of the objective lens unit 74 are as follows. For reasons that will be described in detail later, it is allowed that the distances a and b are different from each other. Here, when drive currents having the same current value and the same polarity are supplied to the first and second actuators 71 and 72, the same drive force is generated. That is, the following relationship holds.

H ₁ = H ₂
As shown in FIG. 3, the focus / tilt control circuit 87 includes a tilt control circuit 877, and the tilt control circuit 877 has an information recording surface 100 a and an optical head 65 of the optical disc 100 that is rotationally driven by the spindle motor 63. A tilt drive signal (tilt drive command value voltage) having a value corresponding to the tilt amount with respect to the optical axis of the upper objective lens 70 is output. Here, for example, a tilt sensor is provided on the optical head 65 of the present embodiment, and a signal indicating the tilt amount between the information recording surface 100a of the optical disc 100 and the optical axis of the objective lens 70 on the optical head 65 is provided. Output from this tilt sensor. As shown in FIGS. 1 and 3, the CPU 90 supplies a signal output from the tilt sensor to the tilt control circuit 877 as a tilt error signal. The tilt control circuit 877 generates the above-described tilt drive signal based on this tilt error signal. That is, it is possible to correct the tilt of the objective lens 70 on the optical head 65 by supplying a drive current corresponding to the tilt drive signal thus obtained to the actuators 71 and 72.

Here, in the optical head of Patent Document 2 (Japanese Patent Laid-Open No. 2003-272203) having a tilt actuator mechanism to which two focus coils are applied, drive currents i ₁ and i ₂ supplied to the two focus coils are as follows. Satisfy the relationship.

i ₁ = i _f -i _t
i ₂ = i _f + i _t
Performs focus driving by the driving current i _f, is it possible to perform tilt driving by the driving current i _t. Here, when the method of Patent Document 2 is applied in the configuration of FIG. 2, the resultant force in the focusing direction y is given by the following equation.

_{f 1 + f 2 = H 1} × (i f -i t) + H 2 × (i f + i t)

_{= H 1 × (i f -i} t) + H 1 × (i f + i t)

= 2H ₁ × i _f
It can be seen that the objective lens (objective lens unit) can be driven in the focusing direction by the above _if . However, when the drive current supply control is applied to the optical head 65 of the present embodiment, from the center of gravity position G of the objective lens unit 74 to the driven positions P ₁ and P ₂ to which the driving forces f ₁ and f ₂ are applied. Since each distance is composed of different distances a and b, the resultant moment in the tilt direction θ has the following relationship.

−f ₁ × a + f ₂ × b = (− H ₁ × a × i ₁ + H ₂ × b × i ₂ ) × cos θ

_{= (- H 1 × a ×} (i f -i t) + H 2 × b × (i f + i t)) × cosθ

_{= H 1 × (b-a} ) × (i f -i t) × cosθ
From the above equation, it can be seen that when the objective lens 70 (objective lens unit 74) is driven in the tilt direction θ, the drive current _if for driving the objective lens 70 in the focusing direction y interferes. In other words, the focus drive and the tilt drive cannot be controlled independently of each other. For this reason, for example, when focus control is performed by the method of Patent Document 2, an unexpected drive force is generated in the tilt direction θ due to interference of the focus drive current, which deteriorates the control performance of the tilt servo and is formed on the track of the optical disc 100. A change in reflected light from a pit or the like is not normally reflected, and a problem that a signal is not normally supplied to the data reproduction circuit 78 is expected.

  Therefore, in the optical disc apparatus 1 of the present embodiment, the design dimensions of the objective lens unit 74 of the optical head 65 main body and the main body of the objective lens unit 74 are considered in consideration of the problem of interference with the tilt drive accompanying the focus drive described above. Based on the relationship between the separation distances a and b acquired in advance by measuring the actual size, focus driving and tilt driving are performed independently in a feedforward manner. That is, in the optical head 65 configured as shown in FIG.

The displacement force in the focusing direction y at the center of gravity G when the displacement force in the tilt direction θ and the focusing direction y is applied to the objective lens unit 74 is avoided so that the influence that the displacement force in the tilt direction θ may have on the displacement force in the tilt direction θ is avoided. drive signal acting on the control of the focusing direction y i _f respectively 1 / a: distributed at a ratio of 1 / b, further adds to the drive current i _t acting the drive signal i _f the control of the tilt direction θ That is, the drive currents i ₁ and i ₂ of the first and second actuators 71 and 72 are obtained. Here, when attention is paid only to the drive current i _f, by supplying the driving current i _f that were allocated at a ratio of above first and second actuators 71 and 72, the driving position by the driving current i _f that were allocated Moments based on the center of gravity G generated at P ₁ and P ₂ are equal to each other. The drive currents i ₁ and i ₂ distributed in this way can be expressed by the following equations [1] and [2].

_{i 1 = (i f / a} -i t) ... the formula [1]
_{i 2 = (i f / b} + i t) ... the formula [2]
Here, the resultant force in the focusing direction y acting on the objective lens unit 74 in this case is given by the following equation.
f ₁ + f ₂ = H ₁ × i ₁ + H ₂ × i ₂

_{= H 1 × (i f /} a-i t) + H 2 × (i f / b + i t)

= H ₁ × (1 / a + 1 / b) × i _f Equation [3]
= H ₂ × (1 / a + 1 / b) × i _f Formula [4]
Further, the resultant moment in the tilt direction θ acting on the objective lens unit 74 satisfies the following relationship.
−f ₁ × a + f ₂ × b = (− H ₁ × a × i ₁ + H ₂ × b × i ₂ ) × cos θ

_{= (- H 1 × a ×} (i f / a-i t) + H 2 × b × (i f / b + i t)) × cosθ

_{= H 1 × (a + b} ) × i t × cosθ ... Equation [5]
_{= H 2 × (a + b} ) × i t × cosθ ... Equation [6]
That is, the focus control of the objective lens unit 74 has the formula [3], by the driving current i _f as shown in Equation [4], also, the tilt control of the objective lens unit 74 has the formula [5], wherein [6] the driving current i _t as shown in, carried out in independent form was.

In the above example, the focusing direction of the drive signal i _f doubled 1 / a and 1 / b times, has been described as being added to the tilt direction of the driving current, the ratio of distribution of 1 / In the present embodiment a: 1 / B, the equivalent ratio b: a, b / (a + b): a / (a + b), k × b: k × a (k: a constant other than 0), etc. it is possible to perform driving and a focus drive independently by i _t and i _f. In any case, how many times the drive signal current finally contributes to the focus drive signal with _respect to the focus drive signal if can be determined according to the specifications required for the drive current circuits 97 and 98 and the optical head 65. Good. Further, when the wavelength of the laser beam is 405 nm, the NA of the objective lens 70 is 0.65, and the substrate thickness of the optical disk 100 is 0.6 mm, the optical disk of the objective lens 70 is set so that the SbER of the reproduction signal is on the order of 10 ^−5. The drive signal current is driven so that the allowable inclination amount of 100 in the perpendicular direction of the recording surface is 0.05 ° × 20 / 2.2 or less.

Based on the above points, the focus / tilt control circuit 87 according to the optical disc apparatus 1 of the present embodiment is configured as follows. That is, as shown in FIG. 3, the focus / tilt control circuit 87 includes a focus control circuit 870, a tilt control circuit 877, an adder (specifically a subtractor) 873 and an adder 874 that function as a drive signal synthesis circuit, Amplifiers (amplifiers / AMPs) 871, 872, 875, 876 are provided. The focus control circuit 870, based on the focus error signal output from the RF amplifier 85, provides a focus drive command value voltage V _f that becomes a drive signal (focus drive signal) in the focusing direction y of the objective lens unit 74 on the optical head 65. Is generated.

Amplifier 871, amplifier 872 amplifies the tilt drive command value voltage V _t of the tilt drive signal output from the tilt control circuit 877. As shown in FIG. 2, the ratios of the amplification factors of the amplifier 871 and the amplifier 872 are the first and _second objects to which the driving forces f ₁ and f ₂ of the actuators 71 and 72 are applied from the gravity center position G of the objective lens unit 74. Corresponding to the separation distances a and b to the drive positions P ₁ and P ₂ , it is set to 1 / a: 1 / b. More specifically, the amplification factor of the amplifier 871 is 1 / a, and the amplification factor of the amplifier 872 is 1 / b. That is, such amplifiers 871 and 872 are

In order to avoid the influence that the displacement force in the focusing direction y at the center of gravity G may have on the displacement force in the tilt direction θ when the displacement force in the tilt direction θ and the focusing direction y acts on the objective lens unit 74. It functions as a driving force adjusting unit that adjusts the distribution of the driving forces f ₁ and f _{2 applied} by the actuators 71 and 72 (of the driving force generating circuits 51 and 52) to the driven positions P ₁ and P ₂ , respectively.

  Here, in addition to the information representing the above equations [1] and [2], the values [a] and [b] of the separation distance are preliminarily stored in the NV-RAM 99 or the like as specific information of the optical head 65 (optical disc). In addition, the variable gain amplifier may be applied to the amplifiers 871 and 872. That is, the CPU 90 refers to the information of the equations [1] and [2] and the information indicating the values [a] and [b] of the separation distance stored in the NV-RAM 99 when driving the objective lens unit 74. Then, the ratio of the amplification factors of the two variable gain amplifiers may be set as appropriate.

Further, as shown in FIG. 3, the adder 873, the output voltage outputted from the amplifier 871, and adds to the tilt drive command value voltage V _t of the tilt control circuit 877 to the opposite sign (output of the tilt control circuit 877 Subtract voltage). Further, the adder 874 adds the tilt drive command value voltage V _t of the tilt control circuit 877 to the output voltage output from the amplifier 872.

The amplification factors of the amplifiers 875 and 876 are, for example, the range and resolution of the focus drive command value voltage V _f output from the focus control circuit 870, the specifications of the drive current circuits 97 and 98 that drive the actuators 71 and 72, and the actuator 71. , 72 is set in accordance with the driving accuracy required for the.

Next, the driving forces f ₁ and f adjusted to be distributed to the first and second driven positions P ₁ and P ₂ on the objective lens unit 74 performed by the optical disk apparatus 1 of the present embodiment configured as described above. The control for assigning ₂ will be described with reference to FIG. Here, FIG. 4 is a flowchart showing processing performed by the focus / tilt control circuit 87 and the first and second driving force generation circuits 51 and 52 of FIG.

As shown in FIGS. 2 to 4, first, the focus / tilt control circuit 87 determines the driving force before the distribution adjustment, which is a reference for giving to the driven positions P ₁ and P ₂ on the objective lens unit 74. A drive signal corresponding to the setting, that is, the driving force before the distribution adjustment is generated. In this case, the focus control circuit 870 generates (outputs) the focus drive command value voltage V _f based on the focus error signal, while the tilt control circuit 877 generates the tilt drive command value voltage V _t based on the tilt error signal. (Output) (S [step] 11).

Next, when the displacement force in the tilt direction θ and the focusing direction y is applied to the objective lens unit 74, the amplifier 871 and the amplifier 872 convert the displacement force in the focusing direction y at the center of gravity position G into the displacement force in the tilt direction θ. As the process for adjusting the distribution of the driving forces f ₁ and f ₂ respectively applied to the first and second driven positions P ₁ and P ₂ so as to avoid possible influences, the respective input focus Focus drive command values V _f1 and V _{f2 in} which the amplification factors of the drive command value voltage V _f are mutually changed are output. That is, the amplifier 871 outputs a tilt drive command value V _f1 obtained by amplifying the focus drive command value voltage V _f by 1 / a times, while the amplifier 872 increases the focus drive command value voltage V _f by 1 / b times. The amplified focus drive command value V _f2 is output (S12).

Further, as shown in FIGS. 3 and 4, the adder 873 adds the tilt drive command value voltage V _t output from the tilt control circuit 877 to the focus drive command value V _f1 output from the amplifier 871 with a reverse sign. to add. On the other hand, the adder 874 adds the tilt drive command value voltage V _t output from the tilt control circuit 877 to the focus drive command value V _f2 output from the amplifier 872. The amplifiers 875 and 876 amplify the voltage input from the adders 873 and 874 sides to generate actuator drive command value voltages V ₁ and V ₂ (S13), and the first and second drive current circuits 97, 98. Drive current circuit 97 and 98, the drive corresponding to the supplied actuator drive command value voltage V _1, V ₂ current _{i 1 = i f / a-} i t, i 2 = i f / b + i t a magnetic circuit 57, 58 (coils 53 and 54). As shown in FIG. 2, the first and second actuators 71 and 72 having the magnetic circuits 57 and 58 (coils 53 and 54) are adjusted in distribution corresponding to the drive currents i ₁ and i _2. The driving forces f ₁ and f ₂ are applied to the first and second driven positions P ₁ and P ₂ of the objective lens unit 74, respectively (S14).

Thus, the focus control of the objective lens unit 74 has the formula [3], as shown in equation [4], the drive current i _f, also, the tilt control of the objective lens unit 74 has the formula [5], wherein [ As shown in FIG. 6], the driving current i _t is performed independently. Therefore, in the optical disc apparatus 1 including the optical head 65 of the present embodiment, suitable drive control of the objective lens 70 is performed while preventing mutual interference between tilt control and focus control of the objective lens 70 on the optical head 65. realizable.

Further, in the optical disc apparatus 1 of the present embodiment, as described above, each of the driven positions P ₁ and P ₂ where the driving forces f ₁ and f ₂ of the actuators 71 and 72 are generated to the gravity center position G of the optical head 65 is provided. The distances are allowed to be different distances a and b. Therefore, the degree of freedom of component layout of the components of the optical head 65 is increased, and thus the optical head 65 having an optimal design mechanically and optically can be obtained.

[Second Embodiment]
Next, description will be made with reference to FIGS. 1 to 4 in which the second embodiment of the present invention is referred to in the first embodiment. FIG. 5 shows processing relating to determination of a suitable ratio of amplification factors of the amplifiers 871 and 872.

  In the optical disk apparatus 1 according to the present embodiment, it is assumed that the amplifiers 871 and 872 in the focus / tilt control circuit 87 included in the optical disk apparatus 1 of the first embodiment are variable gain amplifiers (AMP).

Here, in the optical disc apparatus 301 according to the embodiment, when the displacement force in the tilt direction θ and the focusing direction y acts on the objective lens unit 74, the displacement force in the focusing direction y at the center of gravity position G is displaced in the tilt direction θ. The drive currents i ₁ and i ₂ are supplied to the first and second actuators 71 and 72 so that the influence that may be exerted on the force is avoided.

As described above, the first and second driving force generation circuits 51 and 52 are connected to the first and second driving current circuits 97 and 98, respectively, as shown in FIGS. Drive currents i ₁ and i ₂ having values corresponding to the voltage values (actuator drive command value voltages V ₁ and V ₂ ) are output. Further, as shown in FIG. 2, the first and second actuators 71 and 72 correspond to the values of the drive currents i ₁ and i ₂ output from the first and second drive current circuits 97 and 98, respectively. Driving forces f ₁ and f ₂ are generated respectively.

  In the present embodiment, the amplitude of the reproduction signal (RF signal) obtained through the RF amplifier 85 and the data reproduction circuit 78 is applied to the optical disk on which random data is recorded, for example, at the time of manufacturing the optical head 65. Then, the relationship between the ratios of the amplification factors of the amplifiers 871 and 872 in the focus / tilt control circuit 87 is examined, and the optimum ratio that maximizes the amplitude of the reproduction signal (RF signal) is obtained. The amplification factors of the amplifiers 871 and 872 satisfying the ratio are stored as parameters unique to the device in, for example, the NV-RAM 99 as a storage unit. Further, the CPU 90 reads out the value of the characteristic parameter stored in the NV-RAM 99 when the optical disk apparatus 1 is used (recording / reproducing), and as shown in FIGS. 1 and 3, the amplification corresponding to the read value is performed. The gains of the variable gain amplifiers 871 and 872 are set at a rate. This solves the problem that a suitable amplification factor ratio is not obtained even when the first embodiment is implemented in the case of manufacturing variations.

  Below, the process regarding determination of the ratio of the amplification factor of specific amplifier 871 and 872 is demonstrated. First, the amplification factor search interval Δx is determined from the specification values of the amplification factor resolution of the amplifiers 871 and 872. Hereinafter, as an example, processing for determining a suitable ratio of the amplification factors of the amplifiers 871 and 872 by changing the amplification factor of the amplifier 871 at the search interval of Δx will be described. First, as shown in FIG. 5, by changing the amplification factors of the amplifiers 871 and 872, the amplitude increase flag, which is information indicating that the amplitude of the measured reproduction signal is increasing, is turned off (S21). ). Next, initial values of the respective amplification factors are set so that the ratio of the amplification factors of the amplifiers 871 and 872 becomes 1 / a: 1 / b (S22), and the focus servo is applied to the optical disk on which random data is recorded. The tracking servo is applied (S23). Then, the amplitude value of the reproduction signal (RF signal) is measured (S24). At this time, when measurement is performed for the first time (S25), the amplification factor of the amplifier 871 is changed by Δx (S28), and the process proceeds to S23 and subsequent steps again. If the measurement is performed for the second time or later, the amplitude value of the previous reproduction signal is compared (S26). If the current amplitude value is larger than the previous amplitude value, the amplitude increase flag is turned ON (S27), and the amplifier The gain of 871 is changed by Δx (S28), and the process proceeds to S23 and subsequent steps again. If the current amplitude value is smaller than the previous amplitude value, it is confirmed whether the amplitude increase flag is ON (S29). If it is OFF, the sign of Δx is inverted (S210), and the processing after S23 is performed again. Migrate to If ON, the amplification factors of the amplifiers 871 and 872 are stored in the NV-RAM 99 (S211), and the processing relating to the determination of the amplification factor ratios of the amplifiers 871 and 872 ends.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. Here, FIG. 6 is a block diagram functionally showing the configuration of the optical disc apparatus 301 according to this embodiment. FIG. 7 is a block diagram functionally showing the configurations of the focus / tilt control circuit 387 and the first and second driving force generation circuits 51 and 52 described above included in the optical disc apparatus 301. Further, FIG. 8 is a diagram for explaining the measurement items of the characteristic parameters of the drive current circuits 97 and 98 provided in the optical disc apparatus 301.

  FIG. 9 is a flowchart showing processing relating to measurement of characteristics of the first drive current circuit 97 provided in the optical disc apparatus 301 and registration of the measurement result, and FIG. 10 is a second drive provided in the optical disc apparatus 301. It is a flowchart which shows the process regarding the measurement of the characteristic of the electric current circuit 98, and registration of the measurement result. Further, FIG. 11 is a flowchart showing operation control for correcting the characteristics of the first and second drive current circuits when the optical disc apparatus 301 is used. In the present embodiment, the description will be made with reference to FIGS. 1 to 5 and the like referred to in the first and second embodiments, and in FIGS. 6 to 11, the first embodiment shown in FIGS. Constituent elements that are the same as those applied in the optical disc apparatuses of the first and second embodiments are given the same reference numerals and names, and descriptions thereof are omitted.

  In other words, the optical disc apparatus 301 according to this embodiment replaces the focus / tilt control circuit included in the optical disc apparatus 301 of any one of the first to second embodiments, as shown in FIG. A tilt control circuit 387 is included, and adders 303 and 304 are further provided. The focus / tilt control circuit 387 includes variable gain amplifiers (AMP) 885 and 886 instead of the amplifiers 875 and 876 of the focus / tilt control circuit according to any one of the first to second embodiments.

Here, in the optical disc apparatus 301 according to the embodiment, when the displacement force in the tilt direction θ and the focusing direction y acts on the objective lens unit 74, the displacement force in the focusing direction y at the center of gravity position G is displaced in the tilt direction θ. The drive currents i ₁ and i ₂ are supplied to the first and second actuators 71 and 72 so that the influence that may be exerted on the force is avoided.

As described above, the first and second driving force generation circuits 51 and 52 are connected to the first and second driving current circuits 97 and 98, respectively, as shown in FIGS. Drive currents i ₁ and i ₂ having values corresponding to the voltage values (actuator drive command value voltages V ₁ and V ₂ ) are output. Further, as shown in FIG. 2, the first and second actuators 71 and 72 correspond to the values of the drive currents i ₁ and i ₂ output from the first and second drive current circuits 97 and 98, respectively. Driving forces f ₁ and f ₂ are generated respectively.

In the present embodiment, the optical disk device 301 is generated, for example, at the time of manufacture, by the voltage value of the signal input to each of the first and second drive current circuits 97 and 98 and the input of the signal having this voltage value. A characteristic parameter unique to each drive current circuit indicating the correspondence with the value of the drive current is stored in, for example, the NV-RAM 99 as a storage unit. Further, the CPU 90 reads the value of the characteristic parameter stored in the NV-RAM 99 when using the optical disc device 301 (during recording / reproduction), and as shown in FIGS. 6 and 7, the amplification corresponding to the read value is performed. The gains of the variable gain amplifiers 885 and 886 are set at a rate, and the values of the characteristic parameters are set through the adders 303 and 304, and the actuator drive command value voltages V ₁ and V ₂ are amplified by the variable gain amplifiers 885 and 886. Add to. Thereby, the CPU 90 substantially adjusts the distribution of the driving forces f ₁ and f ₂ respectively applied to the driven positions P ₁ and P ₂ of the objective lens unit 74 based on the above characteristic parameters. .

In the following, processing relating to specific measurement of specific parameters and registration of the measurement results will be described. That is, a method of removing the difference between the undesired driving force offset and the driving gain due to the electrical variation of the driving current circuits 97 and 98 that supply the driving currents i ₁ and i ₂ to the actuators 71 and 72 is as shown in FIG. The relationship between the drive command value voltage applied to each of the drive current circuits 97 and 98 and the drive current is examined at two points or more (examine 97b to 97d and 98b to 98d), and the input / output of each of the drive current circuits 97 and 98 is checked. The relationship is estimated with a linear function. Subsequently, an offset voltage corresponding to the driving signal current 0 [A] and a driving gain corresponding to the slope of the linear function are measured from the linear function, and these are measured in the NV-RAM 99 which is a nonvolatile memory as a parameter for each device. Remember. Then, referring to the characteristic parameters stored in the product use stage, the drive gains g ₁ and g ₂ (slope) of the drive current circuits 97 and 98 are corrected, and the drive current offsets δ _i1 and δ _i2 are set. Corresponding offset voltages V _O1 , V _O2 , (intercept) are applied.

Therefore, first, as shown in FIGS. 8 to 10, when the optical disk apparatus 301 is manufactured, the variable gain amplifiers 885 and 886 are set to have the same amplification factor, for example, 1.0 times, and FIG. As shown in FIG. 9, the drive command value voltage is applied to the drive current circuits 97 and 98 (S41, S51), and the drive command value voltages V ₁ and V ₂ are recorded (S42 and S52). Further, the drive current values I ₁ and I ₂ output from the drive current circuits 97 and 98 are measured (S43, S53), and the drive current values I ₁ and I ₂ at this time are recorded (S44, S54).

As shown in FIGS. 8 to 10, the measurement is performed at least two points for each of the drive current circuits 97 and 98 (measurement points 97b to 97d for obtaining a linear function 97a of the drive current circuit 97, drive current circuit 98 (measurement points 98b to 98d for obtaining a linear function 98a of 98) are measured (S45, S55) and measured a sufficient number of times (S46, S56). Next, the input / output relationship of the drive current circuits 97 and 98 of the actuators 71 and 72 is estimated by the linear functions f ₁ and f ₂ (S47, S57). Next, offset voltages V _o1 and V _o2 corresponding to the drive signal current 0 [A] and drive gains g ₁ and g ₂ which are inclinations of the linear function are measured, and these values are used as NV-specific parameters. It records in RAM99 (S48-S49, reverse order is possible) (S58-S59, reverse order is possible).

When using the optical disk device 301 (when recording / reproducing the optical disk 100), as shown in FIGS. 6, 7, and 11, the CPU 90 refers to the offset voltages V _O1 and V _O2 and the drive gains g ₁ and g ₂ as appropriate. Then, the offset voltages V _O1 and V _O2 are applied to the drive current circuits 97 and 98 so that the driving force is offset by the CPU 90 (S105 to S106, reverse order is possible). Further, the CPU 90 supplies a gain correction value that eliminates the drive gain difference between the drive current circuits 97 and 98 to change the amplification factors of the variable gain amplifiers 885 and 886. For example, when the target value of the drive gain is g, the gains of the variable gain amplifiers 885 and 886 may be set to g / g ₁ times and g / g ₂ times, respectively (S107 to S108, reverse order is possible).

  As described above, in the present embodiment, it is possible to eliminate the difference in the drive current offset between the drive current circuits 97 and 98 and the difference in gain from the command value voltage to the drive current by performing the various adjustments described above. It becomes. In addition, by changing the amplifiers 875 and 876 of the focus / tilt control circuits 187 and 287 to variable gain amplifiers, the correction of the electrical characteristics of the drive current circuits 97 and 98 can be performed using the focus / tilt control circuit 187, The present invention can also be applied to an optical disk device equipped with 287. As other effects, control performance deterioration due to interference between focus drive and tilt drive can be prevented, a control system independent of the focus direction and tilt direction can be designed, and the design freedom of the objective lens actuator can be increased. Therefore, it is possible to reduce the size of the optical head and increase the drive sensitivity to perform high-speed recording / reproduction.

  The present invention has been specifically described above with reference to the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention. For example, the present invention can be applied not only to an optical disk apparatus that records / reproduces an optical disk but also to a drive apparatus that records / reproduces a magneto-optical disk such as a so-called MO.

1 is a block diagram functionally showing the configuration of an optical disc apparatus according to a first embodiment of the present invention. The figure which shows typically the structure of the optical head mounted in the optical disk apparatus of FIG. FIG. 3 is a block diagram functionally showing the configurations of a focus / tilt control circuit and first and second driving force generation circuits included in the optical disc apparatus of FIG. 1. FIG. 4 is a flowchart showing processing performed by a focus / tilt control circuit and first and second driving force generation circuits in FIG. 3. FIG. FIG. 4 is a flowchart showing a procedure for adjusting an amplification factor of a variable gain amplifier so that a reproduction signal amplitude becomes maximum in the focus / tilt control circuit of FIG. 3. The block diagram which shows functionally the structure of the optical disk apparatus based on the 3rd Embodiment of this invention. FIG. 7 is a block diagram functionally showing the configurations of a focus / tilt control circuit and first and second driving force generation circuits included in the optical disc apparatus of FIG. 6. FIG. 7 is a diagram for explaining measurement items of characteristic parameters of first and second drive current circuits included in the optical disc apparatus of FIG. 6. 7 is a flowchart showing processing relating to measurement of characteristics of a first drive current circuit included in the optical disc apparatus of FIG. 6 and registration of the measurement results. 7 is a flowchart showing processing relating to measurement of characteristics of a second drive current circuit included in the optical disc apparatus of FIG. 6 and registration of the measurement results. 7 is a flowchart showing operation control for correcting the characteristics of the first and second drive current circuits when the optical disc apparatus of FIG. 6 is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,301 ... Optical disk apparatus, 51 ... 1st drive force generation circuit, 52 ... 2nd drive current circuit, 53, 54 ... Coil, 55, 56 ... Magnet, 59 ... Elastic support member, 63 ... Spindle motor, 63a ... Rotary encoder, 64 ... Spindle motor control circuit, 65 ... Optical head, 70 ... Objective lens, 71 ... First actuator, 72 ... Second actuator, 73 ... Third actuator, 74 ... Objective lens unit, 74a ... Lens holder, 85 ... RF amplifier, 87, 187, 287, 387 ... Focus / tilt control circuit, 90 ... CPU, 91 ... RAM, 92 ... ROM, 97 ... First drive current circuit, 98 ... Second drive current Circuit 99 ... NV-RAM 100 ... Optical disc 303, 304, 873, 874 ... Adder 870 ... Focus control Circuit, 871,872,875,876 ... amplifier, 877 ... tilt control circuit, 885,886 ... variable gain amplifier.

Claims (8)

An objective lens unit in which an objective lens and a lens holder are integrated;
An elastic support member for displacably supporting the objective lens unit on the optical head body;
Driving equal to the first and second driven positions on the objective lens unit facing each other with the center of gravity position of the objective lens unit supported by the elastic support member sandwiched from the direction orthogonal to the optical axis of the objective lens First and second drive units that respectively apply drive force with efficiency;
In order to avoid the influence of the displacement force in the focusing direction at the center of gravity position on the displacement force in the tilt direction when the displacement force in the tilt direction and the focusing direction is applied to the objective lens unit. An optical disc apparatus comprising: a driving force adjusting unit that adjusts the distribution of the driving force applied to the first and second driven positions by the first and second driving units, respectively.   The driving force adjusting unit adjusts the distribution of the driving force based on the relationship between the distances from the center of gravity of the objective lens unit to the first and second driven positions. The optical disk device according to claim 1.   2. The optical disc apparatus according to claim 1, wherein the driving force adjusting unit adjusts the distribution of the driving force so that the reproduction signal amplitude becomes maximum. The first and second drive units include first and second drive current circuits that output a drive current having a value corresponding to a voltage value of an input signal, and the first and second drive units are configured. Each of the first and second driving force generation circuits for generating a driving force corresponding to the value of the driving current output from each of the driving current circuits,
A characteristic unique to each of the drive current circuits showing the correspondence between the voltage value of the signal input to each of the first and second drive current circuits and the value of the drive current generated from the input of the signal having this voltage value The optical disc apparatus main body further includes a storage unit for storing parameters,
2. The optical disc apparatus according to claim 1, wherein the driving force adjusting unit adjusts the distribution of the driving force based on the characteristic parameter stored in the storage unit. First and second on the objective lens unit opposed to each other with the gravity center position of the objective lens unit having an objective lens supported on the optical head body displaceably sandwiched from the direction orthogonal to the optical axis of the objective lens. Setting a driving force to be applied to each driven position with equal driving efficiency,
Distributing the set driving force so as to avoid the influence of the displacement force in the focusing direction at the center of gravity position on the displacement force in the tilt direction when the displacement force in the tilt direction and the focusing direction is applied. Adjusting steps,
And a step of applying each of the adjusted driving forces to the first and second driven positions, respectively.   In the step of adjusting the distribution of the driving force, the distribution of the driving force is adjusted based on the relationship between the distances from the center of gravity of the objective lens unit to the first and second driven positions. 6. The method of controlling an optical disc apparatus according to claim 5, wherein:   6. The method of controlling an optical disk device according to claim 5, wherein in the step of adjusting the distribution of the driving force, the distribution of the driving force is adjusted so that the reproduction signal amplitude is maximized. The optical disc apparatus includes first and second drive current circuits that output a drive current having a value corresponding to a voltage value of an input signal, and is output from each of the first and second drive current circuits. First and second driving force generation circuits that respectively generate driving forces corresponding to the values of the driving currents, and voltage values of signals input to the first and second driving current circuits, respectively, and the voltage values A storage unit that stores a characteristic parameter unique to each drive current circuit indicating a correspondence relationship with the value of the drive current generated by the input of the signal having,
6. The method of controlling an optical disk device according to claim 5, wherein in the step of adjusting the driving force, the distribution of the driving force is adjusted based on the characteristic parameter stored in the storage unit.

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